1. Field of the Disclosure
The present disclosure relates to an optical disc apparatus, that records data to an optical disc and reproduces data on an optical disc.
2. Description of the Related Art
A variety of types of optical discs such as DVDs or Blu-ray (registered trademark) discs (hereinafter referred to as BDs) are currently used as an information recording medium for storing video and data. From the viewpoint of space efficiency at the time of storage of data, techniques of improving a recording capacity per volume without increasing costs of an optical disc include techniques of improving a track density and techniques of improving a line density.
The technique of improving a track density includes a land (inter-groove)-groove (groove) recording and reproducing technique. This technique has been already used for DVD-RAMs and allows conventional data recoded only in grooves or lands to be recorded on both the groove and the land, and this leads to improvement of a track density. Additionally, a crosstalk cancelling technique is disclosed that reduces a crosstalk component from adjacent tracks (See Patent Document 1, for example). In this technique, a reflected light from an optical disc is divided into and detected as multiple regions, and multiple detected reproduction signals are combined into a reproduction signal with predetermined frequency characteristics by using a waveform equalizer and with the crosstalk component reduced. This technique can further improve the track density.
For a technique of improving a line density, a PRML (Partial Response Maximum Likelihood) signal processing technique is typically used. In order to stably produce the reproduction performance from the PRML signal processing technique, a PLL (Phase Locked Loop) technique capable of supporting a high line density is also used (See Patent Document 2, for example).
With these techniques, improvements have been made in recording capacity of the optical discs.